Method and apparatus for making corrugated board



Jan. 24,1967 w. ATNIKKEL 3,300,359

I METHOD AND APPARATUS FOR MAKING CORRUGATED BOARD Filed Feb. 6, 1962 v 3 2 Sheets$heet' 1 INVENTOR.

\ WILLEM A. NIKKEL BY wwu r PATENT AGENT W. A. NIKKEL Jan. 24, 1967 METHOD AND APPARATUS FOR MAKING CORRUGATED BOARD Filed Feb. 6. 1962 2 Sheets-Sheet 2 INVENTOR. WILLEM A. NIKKEL PATENT AGENT United States Patent Oflice Patented Jan. 24, 1967 3,300,359 METHOD AND APPARATUS FOR MAKING CORRUGATED BOARD Willem A. Nikkei, 729 Greenbrier Ave., Covington, Va. 24426 Filed Feb. 6, 1962, Ser. No. 171,790 14 Claims. (Cl. 156292) This invention relates generally to improvements in a corrugating machine and particularly to improvements in the adhesive applying apparatus of the corrugating machine.

In a corrugating machine manufacturing double faced corrugated board, adhesive is applied in two locations. First, the adhesive is applied at the single facer where the corrugated medium and one liner are bonded together to form single faced board. Second, adhesive is applied at the double backer where the flute tips of the single faced board combine with a second liner to form double faced board. This invention is primarily concerned with the single facer adhesive applicator.

The typical single facer contains two meshing corrugating rolls, and a pressure roll. The meshing corrugating rolls form the corrugated medium, and a nip formed by the pressure roll and one of the corrugating rolls combines the liner with the corrugated medium to form the single faced board.

Two basic approaches are used in the single facer to adhere the liner to the corrugated medium. The first approach applied the adhesive to the peaks of the flutes of the corrugated medium. The second approach applied adhesive to the liner.

The disadvantages of applying the adhesive to the peaks of the flutes of the corrugated medium are well known in the art. The corrugated medium is practically always a very absorbent semi-chemical sheet and the liner a fourdrinier kraft sheet. By applying the liquid adhesive (80% water in the case of starch adhesives) to the more absorbent corrugated medium, the adhesive is allowed to contact and therefore penetrate into the porous corrugated medium for a time interval which is 20 to 30 times longer than the time spa-n allowed for the adhesive to contact the less absorbent liner. This basic error can only mean that appreciably more adhesive must be applied to obtain a reasonable bond to counteract the absorption of adhesive by the corrugated medium. Other disadvantages are caused by the apparatus applying adhesive to the corrugated medium.

The corrugated medium, after being formed in the nip of the corrugating rolls, travels around the circumference of one of the corrugating rolls while being held in mesh with the corrugated surface by a bank of stripper fingers. An adhesive applying roll forms a nip with the corrugating roll and has a surface that is grooved to receive the stripper fingers. Each finger contains in this nip what is called a fluff-out relief which allows the corrugated medium to separate from the corrugating roll. The separation brings the flute tips in contact with the adhesive applicator roll surface whereby the adhesive is transferred to the flute tips. Obviously, adhesive cannot be applied to the corrugating medium in the areas occupied by the fingers. The breaks in the adhesive are frequently As" long and drastically reduce the stacking strength of the single faced board. Failures of this type are characterized by a buckling separation between the corrugated medium and the liner.

The corrugated medium, after the adhesive has been applied, is forced back into the corrugated surface of the corrugating roll by the end of the fluff-out relief. The corrugated medium is often distorted by the fingers during the re-entry, and does not always conform to the corrugated surface of the corrugating roll. The nonconformity results in a variation of the flute size. The irregular flutes eifect the strength of the single faced board that is characterized by poor bonding between the irregular (shorter) flutes and the liner.

The amount of adhesive each flute tip picks up is dependent upon many interrelated factors such as the clearance between the adhesive roll and the corrugating roll, the film thickness of the adhesive on the adhesive roll, the setting of the stripper fingers, the degree of release of the corrugated medium from the surface of the corrugating roll in the fluff-out relief, the effect of changes in machine speed (increases in machine speed increases centrifugal forces which changes the fluff-out characteristics), and the speed relationship between the corrugated medium speed and the surface speed of the adhesive applicator roll. These factors must be taken into account and controlled before proper adhesive transfer is possible. The interrelated factors controlling the adhesive transfer are especially bothersome when the corrugating rolls become defective and must be replaced. The stripper fingers must be carefully repositioned on the surface of the replacement corrugating roll, and the adhesive applicator r-oll must be repositioned with respect to the corrugating roll and the stripper fingers to obtain proper adhesive transfer.

The corrugating industry has long been attempting to develop adhesive applicating methods that would overcome the disadvantages of the methods that applied adhesive to the corrugated medium. Among the various methods that can be classed into the second approach are those that apply adhesive to the liner. Properly designed liner applicators counteract absorption differences, remove fluff-out malfunctions and remove voids caused in the adhesive lines by stripper fingers. Quite obviously, an enormous amount of adhesive would be wasted if applied uniformly throughout the area of the liner. The only practical method of applying the adhesive to the liner is in narrow, cross machine lines that are separated a distance equal to the distance between the peaks of the flutes of the corrugated medium.

Any misalignment between the peaks of the flutes and the narrow lines of adhesive applied to the liner will result in poor bonding. Misalignment can occur in several ways, one of the chief causes being liner shrinkage. The liners are preheated so that the adhesive will set quickly. Since heat causes shrinkage, the liner must be combined with the corrugated medium rapidly after the adhesive application. Otherwise, excessive shrinkage will bring about faulty registering between the peaks of the flutes and the lines of adhesive on the liner.

In addition to misalignment resulting from liner shrinkage, the entire set of lines of adhesive on the liner can be offset in the machine direction so that the lines of adhesive lead or lag the peaks of the flutes of the corrugated medium. This type of misalignment occurs when the surface speed of the adhesive applicator is not synchronized with the surface speed of the corrugated roll, or when the lines of adhesive are not properly registered with the peaks of the flutes.

Controlling the amount of adhesive transferred to the liner has presented additional problems. Some of the liner applicators transferred the adhesive from the peaks of the teeth of a toothed applicator roll, the pitch of the teeth being equal to the distance between the peaks of the flutes of the corrugated medium. Several methods were used to meter the adhesive transferred to the liner from the toothed applicator roll. In some, the metering was accomplished by employing a toothed pickup roll that formed a meshing nip with the toothed applicator roll. The toothed pickup roll was employed to pick up and transfer the adhesive to the peaks of the teeth of the toothed applicator roll. In operation, the transfer was characterized by a stringing of adhesive between the teeth of the pickup roll and the teeth of the applicator roll immediately after the nip which tended to pull the adhesive from the applicator roll, often breaking the lines of adhesive. Also, in such prior art applicators, the adhesive built up in the recessed areas between the teeth and frequent cleaning was necessary to prevent the acumulation of dried adhesive. Heavier applications of adhesive were thrown off the teeth by centrifugal forces, thus limiting the maximum amount that could be transferred to the liner. The minimum amount was controlled by the clearance between the teeth in the nip which introduced critical clearances. Others metered the adhesive by substituting a wiper roll for the meshing toothed roll. Those familiar with roll wipers are aware of the fact that adhesive will build up in the recessed areas between the teeth of the toothed applicator roll. The clearance between the roll wiper and the toothed applicator roll becomes very critical since it controls the amount of adhesive applied to the liner with clearance variations appearing as irregularities in the lines of adhesive, and as irregularities in corrugated board strength.

Still other applied adhesive to the liner from an adhesive applicator roll having narrow, continuous grooves extending axially along the surface. The grooves were separated a distance equal to the distance between the peaks of the flutes of the corrugated medium. The adhesive was removed from the surface areas between the grooves. Those familiar with the operating characteristics of wipers are aware of the difficulty met when attempting to clean the surface of a roll having continuous grooves. The Wiper either smears the adhesive across portions of the surface or removes some of the adhesive from the grooves. Both effects alter the adhesive transfer which appears on the liner as uneven lines of adhesives, and in the single face board as uneven bonding between the liner and the corrugated medium.

The prior art teaches t'he usage of grooved resilient applicator rolls in which a wiper roll was pressed against the surface of the resilient applicator roll. The wiper roll forced some of the adhesive from the grooves of the resilient applicator roll by compressing the surface in the nip. In order to contact the liner with an adhesive remaining within the grooves, it was then necessary to force the liner against the rubber surfaced applicator roll to the extent that the applicator roll was again compressed. Compression of the resilient surfaced applicator roll changed the pitch of the grooves containing the adhesive which resulted in a spreading of the lines of adhesive, and a misalignment of the lines of adhesive with the peaks of the flutes of the corrugated medium.

The prior liner applicator systems attempted to apply the adhesive in unbroken lines. It is felt that the continuous line applicators were resorted to in an attempt to overcome the earlier defect that evolved from the usage of the stripper fingers. Unfortunately, the ability to control the amount of adhesive remaining within the grooves or on the peaks of the toothed rolls was greatly reduced because of the continuous feature.

I have found that the ability to control the amount of adhesive transfer is greatly enhanced by using a hard surfaced applicator having rows of celled (discontinuous) lines and separating the rows of cells a distance equal to the distance betwen ahe peaks of the flutes of the corrugated medium. The amount of adhesive transfered is not controlled by the amount of adhesive contained within the cells but by varying the presure in a nip formed by the applicator roll and a backup roll through which the liner passes. Because of the discontinuous rows, the adhesive, by using a wiper blade, can be efiiciently removed from the surface of the applicator roll without appreciably disturbing the adhesive contained within the cells. The cells are substantially equal in size and contain a substantially constant supply of adhesive, the transfer of which can be easily and positively varied by some 40%.

The cells when designed according to my specifications are thoroughly washed and cleansed frequently during operation without the usage of extra cleansing equipment.

The adhesive, although originally transferred to the liner in a celled pattern, is combined during or after the transfer to form substantially continuous lines of adhesive, thus overcoming the adhesive voids that have been bothersome in the past.

All critical and extremely difiicult to maintain roll clearance and stripper finger settings are eliminated.

In addition, the metering d'ifiiculties associated with the earlier liner applicators have been overcome.

Further, the amount of adhesive required to produce a strong bond can be substantially reduced.

Further advantages of this invention will hereinafter more fuly appear in connection with a detailed description of the drawings in which:

FIG. 1 is a schematic elevational view of the single facer corrugating machine designed according to the invention.

FIG. 2 is a schematic elevational view of another embodiment of the single facer corrugator machine designed according to the invention.

FIG. 3 is an elevational view of the adhesive applicator assembly shown schematically in FIG. 1.

FIG. 4 is a diagram of the control system for the adhesive applictaor assembly shown in FIG. 3.

FIG. 5 is an enlarged fragmentary view of the surface of the applicator roll taken along line 55 of FIG. 3.

FIG. 6 is a fragmentary view of the surface of the applicator roll taken along line 66- of FIG. 5.

Referring to FIGS. 1 and 2, the single facer corrugating machines contain a pair of corrugating rolls 10 and 11. The corrugated surface of the rolls 10* and 11 mesh in the nip 12 through which the corrugated medium A passes and is corrugated. The corrugated medium A travels with the circumference of the corrugator roll 11 through the nip 13 formed by a pressure roll 14 and the corrugating roll 11. A bank of stripper fingers 15 are spaced around the portion of the corrugatin-g roll 11 that contains the corrugated medium A and hold the corrugated medium A in the corrugated surface of the corrugating roll 11. These stripper fingers do not contain a fluff-out relief and therefore the corrugated medium. A cannot become involved in fluff-out malfunctions. The corrugator rolls 10 and 11 and the pressure roll 14- are driven in the direction indicated by a convenient drive means (not shown). Adhesive applicator assemblies, broadly indicated by the reference 16, are placed as close as possible to the nip created by the corrugating roll 11 and the pressure roll 14. Adhesive applied to the liner B will then travel the distance separating the adhesive applicator assembly 16 and the nip 13 quickly thus reducing to a minimum the effects of the shrinkage of the liner B after the application of adhesive thereto.

Referring to FIGS. 1 and 3, the adhesive applicator assembly contains a nip 17 formed by the applicator roll 18 and the backup roll 19. An adhesive pan 2 0 is positioned co-extensive below the axis of the applicator roll 13 so that the height of the adhesive 21 is above the lower reaches of the applicator roll roll 18. A wiper blade asembly 22 is positioned so that the wiper blade 23' contacts the surface of the applicator roll 18 between the adhesive pan 20 and the nip 17. The liner B travels from the adhesive applicator assembly 16 through the nip 13 where heat and pressure adhere the corrugated medium A to the liner B. The single faced board thus produced passes on toward other converting equipment, such as a double backer (not shown).

Referring to FIG. 2, the adhesive applicator assembly 16 is also positioned as close as possible to the nip 13. A backup roll 24 forms a nip 25 with the applicator roll 26. The nip 25 is therefore closely spaced with the nip 13 created by the pressure roll 14 and the corrugating roll 11 so that shrinkage of the liner B will not appreciably affect the location of the adhesive applied in the nip 25. Unlike the applicator assembly of FIG. 1, the applicator assembly of FIG. 2, contains an adhesive pan 27 that performs the dual purpose of applying and metering adhesive 2 8 on the applicator roll 26. The surface of the applicator roll 26 picks up adhesive 28 as it rotates through the adhesive pan 27. The adhesive is metered by the end of the adhesive pan 27 which wipes all but the required amount of the adhesive from the surface of the applicator roll 26. Applicators of this. type are broadly classified as pond-type applicators and are familiar to those having ordinary skill in the art. As will become obvious in the following description, the overall configuration of the adhesive applicator assembly serves as an illustrative means for incorporating the aspects of this invention into a functional adhesive applicator.

Referring to FIG. 1, a first helical gear indicated by the broken lines 29 is attached to and rotates with the corrugating roll 11. A second helical gear 30 is rotatably held by a suitable frame member (not shown) and meshes with the first helical gear 29. A third helical gear indicated by the broken lines 31 is carried by and rotates with the applicator roll 18 and meshes with the second helical gear 30. The helical gears provides a convenient registering means, the importance of which has been brought out in the preceding discusssion. The helical gears 29 and 3d are aflixed to the carrying shafts. The helical gear 31 is adjustably attached to the shaft of the applicator roll 18 so as to be movable inwardly and outwardly along its axis. Since the gears are helical, axial movement of the gear 31 shifts the surface of the applicator roll 18 relative to the surface of the corrugating roll 11 and, therefore shifts the location of the lines of adhesive on the surface of the applicator roll 18 relative to the peaks of the flutes of the corrugated medium A. The registering method is typical of many used in the past and although performing a function important to this invention is not intended to be limiting, but illustrative of a feasible method of assuring the necessary function of proper register adjustment. The same registering apparatus is depicted in FIG. 2.

Before describing in detail the mechanical deployment of the adhesive applicator assembly, the details of the applicator roll 18 will be described, which will give a clearer meaning to the overall layout of the adhesive applicator assembly.

Referring to FIG. 5, which is a fragmentary view of the preferred embodiment of the surface of the applicator rolls 18 and 26, notice that the rows of closely spaced cells 32 are essentially frustrums of square pyramids and have a diagonal extending in a direction substantially perpendicular to the rows of cells along the surface of the applicator roll 18. The rows extend axially along the surface of the applicator roll 18, and are separated a distance substantially equal to the distance between the peaks of the flutes of the corrugated medium A. In the area indicated by the reference 33, the surface of the applicator roll 18 is preferably continuous. The continuation of the surface of the applicator roll 18 between each cell 32 overcomes the tendency of the wiper blade 23 to dip down into the cells which would remove some of the adhesive, bringing about questionable metering qualities and causing uneven wiper blade 23 wear. The cells, when arranged with a diagonal perpendicular to the direction of the row, overcome the tendency of the wiper blade 23 to pull adhesive from the cells onto the surface areas between the rows of cells.

From FIG. 6, notice that the cells 32 are preferably relatively shallow as compared with the diagonal length and have converging side walls 34 that terminate in a bottom surface 35 (frustums of square pyramids). This is to be contrasted with cells that extend into the surface of the applicator roll 18 to the point where the converging side walls intersect (square pyramids) and with cells having side walls that do not converge (cubic). The adhesive will not remain in the preferred embodiment of the cells 32 revolution after revolution of the applicator roll 18, but will be washed out and replaced with fresh adhesive during each passage through the adhesive 21 carried in the adhesive pan 20. The efficient washing action prevents adhesive buildup in the cells 32 which otherwise would eventually harden and reduce the uniformity with which the cells pick up and transfer adhesive tothe liner B. I have found that a satisfactory cell pattern is obtained by using cells 32 having a diagonal length on the surface of approximately 0.070 inch and placing the cells 32 in an array of approximately 12 cells per linear inch. A depth of approximately 0.024 to 0.026 inch will assure eflicient washing action, and will carry suflicient adhesive for bonding the liner B to the corrugated medium A. The cells are substantially equal in volume, and will hold a substantially constant amount of adhesive.

The applicator rolls of FIGS. 1 and 2 are preferably hard surfaced. The hard surface will overcome compression tendencies in the nip formed by the backup rolls 19 and 24, and the applicator rolls 18 and 26, respectively. Compression in the nip would result in a misalignment between the lines of adhesive on the liner B and the peaks of the flutes of the corrugated medium A.

Referring generally to FIGS. 1 and 3 and particularly to FIG. 3, the adhesive 21 in the adhesive pan 20 is picked up by the surface of the applicator roll 18 as it rotates through the adhesive in the direction indicated by the arrow. The surface of the applicator roll 18, as described, contains a mutliplicity of rows of cells, the rows of which are spaced around the surface of the applicator roll 18 a distance equal to the distance between the peaks of the flutes of the corrugated medium A. As the surface of the applicator roll 18 rotates past the edge of the wiper blade 23, the adhesive picked up by the applicator roll 18 is removed from the surface and left within the multiplicity of rows of cells 32. The adhesive is aplied to the liner B in the form of individual droplets as the liner passes through the nip 17. The importance of aligning the lines of adhesive transferred to the liner B with the peaks of the flutes of the corrugated medium A cannot be overstressed and is provided for by the simple registering means explained above.

Referring to FIG. 3, the frame members 36 support fixed bearing blocks 37 that carry the applicator roll shaft 38. It is to be understood that the helical gears 29, 30, and 31 have been omitted from FIG. 3 so that the mechanical deployment of the remaining parts of the adhesive applicator assembly 16 can be clearly shown. The adhesive applicator assembly 16 is made up of two similar frame members 36 that are spaced apart to support the various components of the adhesive applicator assembly. Backup roll arms 33 have one end pivotally attached to the spaced frame members 36 by pins 40. The pins 40 are rigidly attached to the spaced frame members 36 and pass through the backup roll arms 39 which contain suitable bearings 41 that allow the backup roll arms 39 to pivot thereabout. The intermediate portion of the backup roll arms 39 carry backup roll bearings 42 which support the backup roll shaft 43. The opposite ends of the backup roll arms 39 are pivotally joined to a clevis 44 by the clevis pins 45 which pass through the clevis 44 and the backup roll arms 39'. The piston rods 46 of the fluid cylinders 47 are rigidly attached to the clevis 44. The opposite ends of the fluid cylinders 47 are pivotally located by the fluid cylinder pins 48 which pass through the fluid cylinders 47 and the cylinder brackets 49. The cylinder brackets 43 are rigidly mounted to the spaced frame members 36. The fixed bearing blocks 37 carrying the applicator roll shaft 38 are held in place by four bolts 50. In addition, notice that the spaced frame members 36 have cut out portions 7 as indicated by the broken line 51. By removing the bolts 50 from the fixed bearing blocks 37, the applicator roll 18 can be easily replaced by being moved to the left as viewed in FIG. 3. In this manner, a simple, convenient, and rapid means is provided for replacing applicator rolls that have become badly worn.

The wiper blade assembly 22 is positioned on the spaced frame members 36 by the slide block 52. The slide block 52 receives the wiper blade assembly shaft 53. The end portion of the wiper blade assembly shaft 53 contains a short rod 54 that is drilled to receive one end of a tension spring 55. The opposite end of tension spring 55 is attached to a similar rod 56 which is rigidly attached to the slide block 52. Rod 56 is drilled to receive the tension spring 55. The tension spring 55, positioned as viewed in FIG. 3, provides a counterclockwise force in the wiper blade assembly shaft 53. The counter clockwise force holds the wiper blade 23 against the surface of the applicator roll 18. The spaced frame members 36 are slotted, reference 57, to receive and allow movement of the slide block 52 so that the wiper blade assembly moves toward or away from the applicator roll 18 as the slide block 52 moves within the slot toward or away from the applicator roll 18. A screw 58 is rigidly attached to the slide block 52 and a handwheel 59 having internal threading is positioned by, but rotatably free of a fixed plate 60. The handwheel 59 can 'be rotated while being axially held by the fixed plate 60 in the position substantially as shown. The screw 58 passes through a hole in the fixed plate 60 and is free to move axially therein. By turning the handwheel 59, the wiper blade assembly 22 can be moved toward or away from the surface of the applicator roll 18 by the obvious cooperation of the aforementioned handwheel 59, screw 58, slide block 52, and the wiper blade assembly shaft 53. The tension spring 55 forces the wiper blade 23 against the surface of the applicator roll 18 and by turning the handwheel 59 in the proper direction, the wiper blade assembly 22 can be repositioned to maintain a relatively constant wiping action on the applicator roll 18 by the tension spring 55 as required by wear of the wiper blade 23.

From FIG. 3 notice that the adhesive pan 20 is held in position by the rods 61. Adhesive is supplied to the adhesive pan 20 by convenient means (not shown) that replaces the adhesive transferred to the liner B whereby a substantially constant supply of adhesive is contained in the adhesive pan 20. The adhesive pan 20 can be moved to the right, as viewed in FIG. 3, until the left end of the adhesive pan 20 travels beyond the rods 61. The pan can then be lowered down and moved out of the machine. Removal is especially convenient when it is found that hardened adhesive has begun to coat portions of the adhesive pan 20, or when the applicator roll 18 must be replaced.

The adhesive picked up from the adhesive pan 20 covers the entire surface of the applicator roll 18. As the surface of the applicator roll 18 passes by the wiper blade 23, adhesive is removed from the surface of the applicator roll while remaining substantially undisturbed within the cells 32. Since the wiper blade 23 subjects the surface of the applicator roll 18 to substantially constant force (wiping action) as determined by the tension spring 55 and the location of the wiper blade assembly as determined by handwheel 59 setting, the wiper blade 23 is not used to control the amount of adhesive applied to the liner B. The amount of adhesive transferred is controlled by the degree of pressure created in the nip 17 by the fluid cylinders 47 which are connected to the backup roll arms 39.

Referring to FIG. 4, the fluid cylinders 47 are double acting and have fluid lines 62 and 63 entering into the blank ends 64 and the rod ends 65, respectively. The double acting fluid cylinders 47 operate in parallel and have blank ends 64 connected by the lines 62 directly to a 4-way solenoid operated valve 66. The lines 63 connected'to the rod ends 65 of the double acting fluid cylinders 47 are likewise fed into the 4-way solenoid operated valve 66, but, unlike the lines 62, are connected to the 4-way solenoid operated valve 66 after passing through a pressure regulator valve 67 and a pressure gauge 68. The solenoids 69 and 70 of the 4-way solenoid operated valve 66 are connected to a common wire 71 and a main wire 72. The solenoids 69 and 70 can be momentarily energized by the push button switches 73 and 74, respectively, Line 75 leaving the upstream side of the 4-wa solenoid operated valve 66 is an exhaust and line 76 is the pressure line. In the positions shown, the blank ends 64 of the fiuild cylinders are exhausted.

In operation, a predetermined fluid pressure is introduced into the fluid cylinders 47 so that a suitable nip pressure is transmitted through the backup roll arms 39, and the backup roll 19 to the nip 17. Since the amount of adhesive transferred from the applicator roll 18 to the liner B is dependent upon the pressure transmitted to the nip 17 by the fluid cylinders 47, increases in pressure Will increase the amount of adhesive transfer that occurs, and decreases in pressure will decrease the transfer. The pressure can be varied to alter the transfer of adhesive by some 40%. When the unit is not operating, the fluid cylinders 47 are employed to remove the backup roll 19 from the applicator roll 18 by depressing the push button switch 74 which energizes the solenoid 70 of the 4-way solenoid operated valve 66 (in the position shown the fluid cylinders 47 are loading the nip 17). By energizing push button switch 74, the 4-way solenoid operated valve 66 is repositioned so that the blank ends 64 will be pressurized and the rod ends 65 exhausted, thus moving the piston rods 46 upward. Since the backup roll 19 controls the amount of adhesive transferred to the liner B, it forms an important part of this invention.

For optimum control, the backup roll 19 should preferably have a resilient covering such as rubber or plastic. The resiliency will have a tendency to average out any localized high pressure zones in the nip formed by the applicator roll and the backup roll that results from slight machinery inaccuracies, or from localized differences in the thickness of the liner. Any foreign matter carried by the liner, or picked up by either roll, when passing through the nip will compress the resilient surface of the backup roll instead of damaging the hard surface of the applicator.

The adhesive will be picked up by the liner B in the form of individual droplets, one from each cell. The droplets, when the cells are designed according to the description set forth herein, will quickly unite to form a continuous line of adhesive or will remain separated by a minute distance that will not aifect the strength of the corrugated product. The amount of adhesive transferred to the liner B is controlled by the pressure exerted on the applicator roll 18 by the backup roll 19 in the nip 17. The wiper blade 23 functions as a means for removing the adhesive from the surface of the applicator rolls and does not control the amount of adhesive contained within the cells 32. The adhesive, although greatly reduced in quantity as compared with earlier systems forms a bond between the liner and the corrugated medium that is equal or superior to the bond formed in earlier systems. The earlier systems used considerable amounts of adhesive which did not actually form a bond, but either soaked into the corrugated medium or dried on the liner without contacting the peaks of the flutes of the corrugated medium (wide lines of adhesive applied to the liner didnt contact the relatively narrow flute tip).

Many modifications of the embodiments disclosed herein are possible that still reside within the basic scope of this invention as set forth in the claims below.

I claim:

1. In a method of making paperboard comprising the steps of contacting a liner with the outer periphery of a rotating applicator roll, applying rows of spaced droplets of an adhesive bonding agent to the liner from rows of discrete cells on the applicator roll in a manner so that the rows extend transversely across the liner, forming a line of bonding agent from each row by combining the spaced droplets in each row while the droplets are on the liner, then contacting each line of bonding agent with the peak of a flute on a corrugated medium, and then curing the bonding agent to form a bond between the flute peaks and the liner.

2. In a method in accordance with claim 1, wherein the cells are frustum pyramid-shaped recesses on the outer periphery of the applicator roll, and applying said droplets to said liner only from the cells, with the amount of bonding agent in each droplet being less than the quantity which may be contained within the cells, and automatically refilling the cells with the bonding agent as the applicator roll rotates.

3. A method in accordance with claim 1, including the step of varying the amount of bonding agent transferred to the liner from said cells by adjusting the force with which a back-up roll holds the liner against said applicator roll thereby varying the nip pressure between said applicator roll and said liner.

4. An adhesive applicator assembly for applying adhesive to a liner in a corrugating machine comprising:

(a) a pair of spaced frame members,

(b) a hard surfaced applicator roll carried between said spaced frame members,

(c) said hard surfaced applicator roll having a surface containing a multiplicity of parallel rows of discrete cells extending axially along the surface thereof,

(d) a backup roll carried between said spaced frame members, forming a nip with said hard surfaced applicator roll,

(e) means for forcing the backup roll against said hard surfaced applicator roll,

(f) means for adjusting the force with which said backup roll is held against said hard surfaced applicator roll,

(g) means for applying a substantially constant amount of adhesive to the hard surfaced applicator roll,

(b) means for passing a liner through the nip formed by the hard surfaced applicator roll and the backup roll, whereby said liner picks up adhesive from the cells on the surface of said hard surfaced applicator roll,

(i) and means for driving the hard surfaced applicator roll at a speed synchronized with the speed of movement of the liner.

5. An adhesive applicator assembly for applying adhesive to a liner in a corrugating machine in accordance with claim 1 wherein said cells are truncated pyramids having their largest cross-sectional area at said surface of the applicator roll, and said cells having their diagonals substantially parallel to the longitudinal axis of said applicator roll.

6. In a corrugating machine in accordance with claim 4 including means for corrugating a medium to be adhesively joined to the liner, and means for driving said applicator roll at a speed synchronous with the speed of said corrugating means, and the distance between adjacent rows of cells being substantially equal to the distance between the peaks on adjacent flutes of the corrugating means.

7. The apparatus according to claim 5 in which the diagonals of the cells are approximately 0.070" long, said cells arranged in an array of approximately 12 cells per linear inch.

8. In a corrugating machine having a pair of meshing corrugating rolls for forming a corrugated medium, a superimposed pressure roll forming a nip with one of said corrugating rolls and adhesively bonding a liner to the peaks of the flutes of the corrugated medium, the improvement in an adhesive applicator assembly comprismg:

(a) a pair of spaced frame members supporting said meshing corrugating rolls and said superimposed pressure roll therebetween,

(b) fixed bearing blocks carried by the spaced frame members,

(0) a hard surfaced applicator roll carried between the spaced frame members by the fixed bearing blocks in proximity of the nip formed by the pressure roll and one of the corrugating rolls,

((1) said hard surfaced applicator roll having a surface containing a multiplicity of parallel rows of shallow frustum shaped cells of square pyramids extending axially along the surface thereof, the cells in each row having diagonals extending in a direction substantially perpendicular to the direction of the row,

(e) said rows of cells equally spaced on the surface thereof a distance substantially equal to the distance between the peaks of the flutes of the corrugated medium,

(f) backup roll arms pivotally attached to the spaced frame members,

(g) a backup roll rotata-bly carried above the axis of the hard surfaced applicator roll by the backup roll arms,

(h) means mounted on the backup roll arms for forcing the backup roll against the hard surfaced applicator roll,

(i) means for adjusting the force with which the backup roll is held against the hard surfaced applicator roll,

(j) an adhesive pan positioned below the axis of the hard surfaced applicator roll, said adhesive pan having side walls extending above the lower reach of the applicator roll whereby adhesive is applied to the surface of and into the cells of the hard surfaced applicator roll,

(k) a wiper blade assembly carried by the spaced frame members having a wiper blade contacting the surface of the hard surfaced applicator roll,

(1) resilient means forcing the wiper blade against the hard surfaced applicator roll, whereby said wiper blade removes adhesive from the surface of the hard surfaced applicator roll without appreciably disturbing the adhesive contained within the cells,

(In) means for driving the hard surfaced applicator roll at a surface speed substantially synchronous with the surface speed of the pair of meshing corrugating rolls,

(n) means for passing the liner between the hard surfaced applicator roll and the resilient backup roll whereby lines of adhesive will be transferred from the cells to the liner,

(0) and means for registering the multiplicity of rows of cells with the peak of the flutes of the corrugated medium, whereby the lines of adhesive transferred to the liner from the cells will contact the peaks of the flutes of the corrugated medium.

9. The apparatus according to claim 8 in which the backup roll is resilient surfaced.

10. In a corrugating machine having a pair of meshing corrugating rolls for forming a corrugated medium, a superimposed pressure roll forming a nip with one of said corrugating rolls and adhesively bonding a liner to the peaks of the flute-s of the corrugated medium, the improvement in an adhesive applicator assembly comprising:

(a) a pair of spaced frame members supporting said meshing corrugating rolls and said superimposed pressure roll therebetween,

(b) fixed bearing blocks carried by the spaced frame members,

(c) a hard surfaced applicator roll carried between the spaced frame members by the fixed bearing blocks in proximity of the nip formed by the pressure roll and one of the corrugating rolls,

(d) said hard surfaced applicator roll having a usrface containing a multiplicity of parallel rows of shallow frustum shaped cells of square pyramids, extending along the surface thereof, the cells in each row having diagonals extending in a direction substantially perpendicular to the direction of the row,

(c) said rows of cells equally spaced on the surface thereof a distance substantially equal to the distance between the peaks of the flutes of the corrugated medium,

(f) backup roll arms pivotally attached to the spaced frame members,

(g) a backup roll rotatably carried substantially below the axis of the hard surfaced applicator roll by the backup roll arms,

(h) means mounted on the backup roll arms for forcing the backup roll against the hard surfaced applicator roll,

(i) means for adjusting the force with which the backup roll is held against the hard surfaced applicator roll,

(j) an adhesive pan positioned co-extensive substantially above the axis of the hard surfaced applicator roll, said adhesive pan having a wall formed by a portion of the surface of the hard surfaced applicator roll,

(k) said adhesive pan having another wall terminating against the surface of the hard surfaced applicator roll, said termination removing adhesive from the surface of the hard surfaced applicator roll without appreciably disturbing the adhesive contained within the cells as the hard surfaced applicator roll rotates thereby,

(1) means for driving the hard surfaced applicator roll at a surface speed substantially synchronous with the surface speed of the pair of meshing corrugating rolls,

(In) means for passing the liner between the hard surfaced applicator roll and the backup roll, whereby lines of adhesive will be transferred from the cells to the liner,

(n) and means for regsistering the multiplicity of rows of cells with the peaks of the flutes of the corrugated medium, whereby the lines of adhesive transferred to the liner from the cells will contact the peaks of the flutes of the corrugated medium,

11. The apparatus according to claim 10 in which the diagonals of the cells are approximately 0.070" long, said cells arranged in an array of approximately 12 cells per linear inch.

12. The apparatus according to claim 10 in which the surface of the hard surfaced applicator is continuous between each cell.

13. In a corrugating single facer machine including a pair of intermeshing corrugating rollers for forming a series of regularly spaced corrugations in a continuous web of corrugating medium and a pressure roller forming a pressure nip with one of said corrugating rollers, the improvement comprising means for applying individual droplets of a bonding agent to a continuous web of liner material in rows extending transversely of said web of liner material and spaced apart a distance equal to the spacing of the corrugations formed in said medium, said means including an applicator roll having a plurality of parallel rows of discrete cells on its periphery extending in an axial direction.

14. In a corrugating machine in accordance with claim 13 with each cell being a frustum of a pyramid with its largest cross-sectional area at the periphery of said ap plicator roll, each row having approximately twelve cells per linear inch, the depth of the cells being approximately .024 to .026 inch, the diagonal length of said cells being in a direction substantially parallel to the longitudinal axis of the applicator roll, and each cell diagonal being approximately .07 inch long.

References Cited by the Examiner UNITED STATES PATENTS Re. 22,842 2/1947 Hill l56205 1,135,509 4/1915 Ferres 156473 X 1,793,082 2/1931 Goss 118-212 2,051,296 8/1936 Goettsch 156473 I 2,051,319 8/1936 Sieg 156472 X 2,290,200 7/1942 Murch et al 118-12 2,531,036 11/1950 Goettsch l18212 2,876,734 3/ 1959 Nitchie 1l8249 2,940,868 6/1960 Patchell 117-1 11 3,036,927 5/1962 Jerothe 117-7 EARL M. BERGERT, Primary Examiner. J. I. BURNS, H. EPSTEIN, Assistant Examiners. 

1. IN A METHOD OF MAKING PAPERBOARD COMPRISING THE STEPS OF CONTACTING A LINER WITH THE OUTER PERIPHERY OF A ROTATING APPLICATOR ROLL, APPLYING ROWS OF SPACED DROPLETS OF AN ADHESIVE BONDING AGENT TO THE LINER FROM ROWS OF DISCRETE CELLS ON THE APPLICATOR ROLL IN A MANNER SO THAT THE ROWS EXTEND TRANSVERSELY ACROSS THE LINER, FORMING A LINE OF BONDING AGENT FROM EACH ROW BY COMBINING THE 